Sentence generation

[Edward Ned Harvey (patternforpython)]

I am working on a random sentence generator, specifically designed for cryptographic strength, using short, easily memorized, easily typed words. The purpose is to make it easy for normal humans to learn (and happily use) strong passphrases. For example, the following both have approximately equal cryptographic strength, but the latter is much easier to remember and type:

yMFwNgJI
vs.
Fat apes tied 7 furs

The two challenges that I'm finding very difficult to overcome are to find a grammar definition, and find an annotated word list that has enough detail to play nicely with the grammar definition. For example, nouns need to be categorized into the various types of nouns, and verbs need to be categorized into action, stative, transitive, etc... And the grammar needs to know that only transitive verbs take a direct object, and stuff like that, so we don't end up generating sentences that violate obvious grammar rules. Or else we might as well just generate random words, which are much harder to remember than random sentences.

Anybody have a suggestion on how to find a grammar definition and word list to use it on?

Thanks...